Computing technology began with a computing model consisting of a central processor performing all computational functions within a computer system. This model has changed over the years, and although still very relevant to certain applications, other computing models have been developed.
One current computing model is a distributed processing system. This computing model includes multiple processors that are interconnected by a network. Computing tasks are distributed among the processors as application requirements demand.
The distributed computing model has been applied to the industrial process control environment. Advantageously, this computing model facilitates higher reliability and increased system throughput, yielding improved process control. One example of an industrial process control system adhering to a distributed computing model is the "I/A Series" system from The Foxboro Company of Foxboro, Mass., USA.
The components of an example I/A Series system are depicted in FIG. 1. A server 17 provides database and control functions for the distributed processing system. Server 17 may be an I/A Series system model "AP" or "AW" server executing a "Solaris" Operating System ("OS") 21. A database 23 operates in connection with server 17. A "Nodebus" network 15 interconnects elements within the distributed processing system.
A Control Processor "CP" 11 is attached to Nodebus 15, and provides, e.g., process input/output ("I/O") functions. For example, CP 11 could include analog-to-digital converters for reading sensor data.
One operational issue in distributed processing systems is the distribution of software among the processors. In the I/A Series system of FIG. 1, server 17 includes a boot server 19 software component that is responsible for providing CP 11 with initial software, e.g., an operating system. Database 23 includes operating system images 25 for different CPs 11. In regard to initial software loading, CP 11 includes a bootstrap ROM 13 and a mechanically configurable identifier, i.e., a "letterbug" 27 for identification purposes. Letterbugs are more completely described in U.S. Pat. No. 5,006,842, entitled "Identity Insert Blocks for Electronic Modules", and issued on Apr. 9, 1991, which is hereby incorporated by reference herein in its entirety.
The boot process for CP 11 within the above described I/A Series system is described below with reference to the flow-diagram of FIG. 2. To begin, CP 11 is powered on or reset, STEP 101. A processor within CP 11 begins booting from a bootstrap loader within ROM 13, STEP 103. During execution of the bootstrap loader, the processor within CP 11 reads letterbug 27 such that the identity of CP 11 is established, STEP 105.
Once letterbug 27 has been read, CP 11 broadcasts a boot request containing letterbug 27 over Nodebus 15, STEP 107. Server 17, and all other servers on Nodebus 15, receive the boot request, STEP 109. A server (e.g., server 17) assigned to the particular letterbug 27 of CP 11 retrieves a corresponding boot image 25 from its database 23, STEP 111. The boot image is transmitted to CP 11, STEP 113, and CP 11 boots therefrom, STEP 115. As one example, in the "I/A Series" system, the boot image is that of a "VRTX" type embedded operating system, available from Microtec Research of Santa Clara, Calif., USA.
In some distributed computing systems it may be desirable to have processing nodes that lack mechanically configurable identifiers. Furthermore, these "identifierless" nodes may coexist in a system with nodes having mechanically configurable identifiers. This introduces difficulties with identification of the "identifierless" nodes, and difficulties in managing the boot image loading of such "identifierless" nodes through a common, system wide, boot image server.
The present invention is directed toward solutions to the above-noted problems.